That´s an really interesting question...First time I heard about differences with this unit, so I looked through my guts and indeed, there was indeed even a change in the pcb layout. But this change already occured during the script era.

So I think between the late script-era and the block-era will not be a big difference. I have to check that out sometime...

analogguru

There´s a sucker born every minute - and too many of them end up in the bootweak pedal biz.

The only difference in the audio section are the tropical fish caps and the 22k resistors instead of the white film and 20k resistors. I don´t believe that the difference between 22k and 20k will have a big influence, since this can also result from capacitor tolerances (10% - 20 %).

The feedback resistor (intensity) of 15k seems to have been changed in 1978, maybe earlier.

Alltogether it appears that the - not real significant -change has occured earlier in the script era and not together with the script/block change.

The old ones can be recognized on the tropical fish and that the wire holes are symmetrical in the middle of the pcb-edge.

analogguru

There´s a sucker born every minute - and too many of them end up in the bootweak pedal biz.

So the script version and the later ones ARE different!!Got one in for repair and traced it! Main differences are the clean mixing circuit, some small resistor changes in the LFO and the resistor value in the Vref

Is this traced from a script Phase 100? The one with the "tropical fish" coloured capacitors?

So the script version and the later ones ARE different!!Got one in for repair and traced it! Main differences are the clean mixing circuit, some small resistor changes in the LFO and the resistor value in the Vref

Is this traced from a script Phase 100? The one with the "tropical fish" coloured capacitors?

I've just bought a fairly old block logo Phase 100, which has clearly seen better days. I plan to get it back to full working order and maybe do some small mods as well. Looking at the schematic, I really don't get why there are four extra stages which aren't modulated by the LFO, as these will not contribute anything to the phasing effect. I even wonder if they did it pourely as a marketing gimmik, to advertose it as a 10-stage phaser, when in reality it's only a six-stage. I would be interested if anyone has any thoughts or insite on this.

zaphod wrote:Looking at the schematic, I really don't get why there are four extra stages which aren't modulated by the LFO, as these will not contribute anything to the phasing effect. I even wonder if they did it pourely as a marketing gimmik, to advertose it as a 10-stage phaser, when in reality it's only a six-stage.

The Phase 100 is a 10 stage phaser.Pedal manufacturers are not in the market to include components in their designs that serve no purpose.

The stages you are referring to are "fixed" stages. Fixed stages do contribute to the overall phasing effect.

zaphod wrote:Looking at the schematic, I really don't get why there are four extra stages which aren't modulated by the LFO, as these will not contribute anything to the phasing effect. I even wonder if they did it pourely as a marketing gimmik, to advertose it as a 10-stage phaser, when in reality it's only a six-stage.

The Phase 100 is a 10 stage phaser.Pedal manufacturers are not in the market to include components in their designs that serve no purpose.

The stages you are referring to are "fixed" stages. Fixed stages do contribute to the overall phasing effect.

I still don't see the point, since there's no modulation being applied to the phase shift. So yes, while I agree a phase shift is happening in those stage, the shift is still not being swept in any way, and it's that sweep which the human ear detect.

Disclaimer: I'm an EE with severe OCD, so I like to dig into what's really going on inside FX pedals. So please feel free to set me straight on what I just said, and I realy won't mind.

That article has a pretty good summary of textbook flanger and phaser theory. R.G. Keen writes some great articles. What's interesting is that he seems to be agree with me on some important points.

It turns out that the human ear is not too sensitive to phase shifts...

The most common commercial phase shifters stop with four stages (such as the MXR Phase 90, Univibe) or six stages (MXR phase 100).

...although the effect is noticeable, it's much better if the notches move up and down in frequency.

So while I might gree that maybe there's some benefit in having some extra fixed phase shift stages, it's really not clear how much of a benfit that really is. Maybe it becomes more useful when feedback is switched on...? Even then, wouldn't it make more sense if different RC values were used in each of the fixed stages to enhance the effect...?